Bicycle Mechanics - Spacing Dimensions for Chainrings and Cassettes

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MTBaddict
02-14-09, 07:50 AM
What is the center-to-center distance between chainrings on a MTB triple crankset?

What is the center-to-center distance between cogs the 9-speed cassette?

Thanks in advance!

pacificaslim
02-14-09, 08:37 AM
try looking it up on www.sheldonbrown.com
DaveSSS
02-14-09, 08:51 AM
Shimano 9 cogs are spaced 4.32mm. Sheldon seems to be off on his chainring spacing. I've checked several 9/10 speed cranks and they all measure in the 7-7.5mm range. Sheldon mentions something about 5mm (IIRC), which is not even close.

pacificaslim
02-14-09, 11:29 AM
I have a Deore triple on one bike and to the naked eye with a tape measure, it looks like about 6mm to me. It does look more than 5mm, but not as high as 7mm center to center on this particular chainring set.

It's very hard to measure. I'll try to come up with an accurate method.
DaveSSS
02-14-09, 03:18 PM
The best way is to take the crank off, lay it on a smooth flat surface and use a machinist's scale to measure tip to tip. It should be very close to 7.5mm. Even a new Campy 11 speed crankwith the rings .6mm closer still meausure about 7mm.

Note that the teeth are not always centered with respect to the mounting surfaces.